Hi @sachin! There’s no API that will capture the actual email content itself, but you can get a link to the invoice and include that within your own email communication.
When creating an invoice on your Seller Dashboard, you should have the option to select to share “Manually”. Selecting this means that Square will not email the invoice automatically. You can then use the Invoices API to retrieve that invoice. Invoice objects have a public_url field which you can use to link the customer to the Square-hosted invoice page from your own email.
